The present invention relates to a tube-type heat exchanger and, more particularly, to a tube-type heat exchanger having a core with a spiral baffle around the core.
Tube-type heat exchangers are commercially available wherein a medium flows through the pipes in the pipe bundle and another medium is passed around the pipes by means of baffle plates in such a way that this latter medium always flows transversely into the pipe bundle. The number of baffle plates determines the number of transverse currents. The best known of these heat exchangers consist of sectional or annular partitions. These known heat exchangers have the disadvantage that, as the medium is deflected, longitudinal currents and, in particular, dead spaces are formed which have a detrimental effect on the heat exchange. Moreover, energy is expended in the lengthy deflecting operation, thus resulting in a loss of pressure. As a result of the pressure head which builds up during deflection, so-called by-passes are produced at the pipe passages and between the baffle plates and the casing of the heat exchanger, thus reducing the heating efficiency.
A tube-type heat exchanger of the kind described at the beginning is known from DT-PS No. 809 816. The spiral arrangement of the baffles proposed in this specification is intended to permit a counterflow heat exchange of gas and condensate with simultaneous condensation in the heat exchanger, which is used as a condensation cooler, while ensuring a good separation of the gas flowing upward and the condensate flowing downward, so as to ensure that the gas current interferes as little as possible with the downward flow of condensate. This known heat exchanger consists essentially of four separate parts, a tubular casing, a core, a baffle spiral pushed onto the core, and a pipe bundle passing through holes provided in the baffle spiral. The bores for the individual pipes have to be provided in inclined surfaces and must be axially aligned with one another for each pipe. This construction is therefore relatively complicated and expensive to produce, particularly when made to order, primarily because the spiral has to have more coils. When the apparatus is produced for stockpiling, correspondingly large and expensive storage space is required. In the region of the tubular core, there are relatively large dead spaces in which the heat exchange is minimal. This is true particularly of small diameter heat exchangers with a consequently smaller number of annular cooling pipe arrangements. This results in a reduction in the heating efficiency.
An aim of the present invention therefore is to construct a heat exchanger of the type described above having spiral baffles, in such a way that manufacture can be simplified, particularly in the case of apparatus made to order, and so that the efficiency of the heat exchanger is also improved.
In one aspect of the invention individual, one-piece basic elements are provided, each comprising an integrated core member and spiral baffle member. These basic elements are the same for all sizes and can be assembled to form longer lengths as required, i.e. depending on the requirements and performance of the heat exchanger. By virtue of the fact that the core member and baffle member are integral, the holes required for the cooling or heating medium pipes can be produced in the same casting operation as for the basic elements. Moreover, it is also relatively easy to provide these holes at a later stage due to the shortness of the basic elements and the integral spiral. The fact that casting processes can be used adds considerably to the range of suitable materials. In particular, light casting materials, such as aluminum and aluminum compounds, may advantageously be used, so as to reduce the weight of the apparatus. The production costs can be significantly reduced by using the solution according to the principles of the invention. Storage problems are substantially reduced because only uniform basic elements which can be put together to form larger units have to be stored. Apparatus can be manufactured to order without any additional expense.
Moreover, the use of spiral baffle members has the advantage that the medium to be cooled or heated always flows transversely to the pipes through the heat exchanger, without being deflected. In this way, the above mentioned disadvantages of the commercially available heat exchangers are eliminated and optimum heat exchange is obtained.
Another advantageous feature of the present invention is that the core member is stepped to permit simple, rapid and satisfactory assembly of the basic elements to form larger units. The steps of the core member also preferably are arranged to result in a practically seamless transition from one basic element to another when the elements are assembled to form larger units.
In the case of a spiral with one complete coil, the spiral end surfaces also may be axially aligned with one another and alignment of the basic elements can be made substantially easier or may even be unnecessary, since in the preferred construction of the present invention the spiral ends of adjacent ends of the basic elements abut on one another, which permits fixing in the peripheral direction.
In the present invention dead spaces may be reduced and the heat exchange is improved to an optimum level by axial ribs on the core.
These and other objects, features and advantages of the present invention will be more clearly understood through a consideration of the following detailed description.